The invention concerns an arrangement which has a waveguiding, laser active, epitaxial layer on a substratum and a process for making same.
Lasers can be well integrated into optical circuits as light sources or light amplifiers when the laser active region has the form of an optical waveguide. In the case of solid state lasers, it is necessary that the laser-active material be manufacturable as a thin layer or strip on a substratum which refracts to a lesser extent than the layer itself.
From the publication by H. G. Danielmeyer, entitled "Problems in Solid State XV" (1975), pp. 253-277, stoichiometric neodymium laser substances are known which possess a high degree of light amplification. Lasers which are made from these materials can be miniaturized into lengths having a dimension about 1 mm.
From this same publication, the laser material, neodymium penta-ultraphosphate (NdP.sub.5 O.sub.14) is known. This material has, in addition to a high amplification capacity, excellent spectral laser qualities and an unlimited operational life. This material possesses, however, the disadvantage that it forms mildly ferroelastic twinning domains. These domains act as scattering centers optically and can thereby disturb a stable laser operation.
From the Publication by H. G. Danielmeyer, J. P. Jeser, E. Schroenherr, and W. Stetter, in the Journal of Crystal Growth (1975) pp. 298- 302, it is known that neodymium ions can be partially replaced by yttrium ions. Thus, the laser quality of neodymium penta-ultraphosphate can be improved, since the formation of twinning domains in then prevented.
This last mentioned document also discloses a technique for growing crystals of neodymium penta-ultraphosphates. Up until now, it was, however, not possible to manufacture waveguide lasers from this material, because suitable substrates were unknown.